There are three types of inductors namely thin film type inductors, multilayered type inductors, and wire wound type inductors, which are commercially available.
TW patent NO. 1430300 discloses a multilayered type inductor which includes a plurality of insulator layers, and a plurality of patterned metal layers. The insulating layers and the patterned metal layers cooperatively define a core and a coil of the multilayered type inductor.
A method of making the multilayered type inductor includes the steps of: plating the patterned metal layers on the corresponding insulating layers; forming holes in each of the insulating layers; and filling a conducting material into the holes such that the patterned metal layers are electro-connected to one another through the conducting material.
The aforesaid method is relatively complicated. In order to simplify both the structure of the multilayered type inductor and the method of making the same, TW patent application publication NO. 201440090 A discloses a multilayered type inductor 10 (see FIG. 1) and a method of making the same.
The method of making the multilayered type inductor includes the steps of: laminating a first circuit plate 110, a second circuit plate 120, a third circuit plate 130 and a fourth circuit plate 140 (see FIG. 2A); attaching an assembly of a supporting film 150 and a bonding pad circuit 160 to the first circuit plate 110 (see FIG. 2B); transferring the bonding pad circuit 160 from the supporting film 150 to the first circuit plate 110 (see FIG. 2C); removing the supporting film 150 from the bonding pad circuit 160 (see FIG. 2D); sintering the first, second, third and fourth circuit plates 110, 120, 130, 140 and the bonding pad circuit 160 so as to form a multilayered substrate 100 (see FIG. 2E); and scribing the multilayered substrate 100 using a scriber 170 (see FIG. 2F), such that the multilayered substrate 100 can be broken into a plurality of multilayered type inductors 10 (see FIG. 1).
Referring to FIG. 1, each of the first, second, third and fourth circuit plates 110, 120, 130, 140 includes a respective one of non-magnetic bodies 111, 121, 131, 141 and a respective one of first, second, third and fourth circuit patterns 112, 122, 132, 142. Formation of the first, second, third and fourth circuit plates 110, 120, 130, 140 requires numerous steps (a total of at least 13 steps), including punching each non-magnetic body 111, 121, 131, 141 to form the holes, filling the conductive paste in the holes, forming the first, second, third and fourth circuit patterns 112, 122, 132, 142 and sintering, before laminating the first, second, third and fourth circuit plates 110, 120, 130, 140.
The aforesaid method is relatively complicated, and the bonding strength between the first, second, third and fourth circuit patterns 112, 122, 132, 142 may be insufficient.
Besides, undesired non-ohmic contact and Joule-heating may be induced at the interfaces between every two adjacent ones of the first, second, third and fourth circuit patterns 112, 122, 132, 142.